Worms from Hell? Deepest Multicellular Life Found

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How low can worms go? According to a new study, at least 0.8
miles (1.3 kilometers) below the Earth's surface.

That's the depth at which scientists discovered a new species of
worm, dubbed Halicephalobus mephisto in honor of Faust's
demon Mephistopheles. The worm, reported this week in the journal
Nature, is the
deepest living multicellular organism ever found.

"We tried to get the title of the paper to be 'Worms from Hell,'"
said study author Tullis Onstott of Princeton University. "But
Nature didn't go for that."

The Moby Dick worm

Onstott and his colleagues have been searching for subsurface
life for 15 years, focusing on the ultra-deep mines of South
Africa, which penetrate more than 1.8 miles (3 km) into the
Earth. They and other teams of scientists have found that life
has very deep roots, with single-celled organisms found miles
underground. Some of these organisms are quite extreme: One 2008
study found life thriving
a mile under the seafloor, surviving in temperatures between
140 and 212 degrees Fahrenheit (60 and 110 degrees Celsius).
[Read
Extremophiles: World's Weirdest Life ]

But finding the multicellular, 0.02-inch-long (0.5 millimeters)
H. mephisto is a different story. The worm, or nematode,
lives in fluid-filled rock fractures, where it grazes on
bacteria, Onstott told LiveScience.

"It's kind of like finding Moby Dick in Lake Ontario," he said.
"It's so volumetrically big. It's 10 billion times the size of
the bacteria upon which it feeds."

To find the worm, Onstott and his team sampled water from mine
boreholes as deep as 2.2 miles (3.6 km). They also sampled soil
around the mine boreholes and filtered about 40,000 gallons of
surface water to ensure that the nematodes weren't coming into
the mine from above.

In the Beatrix gold mine, they found their quarry: the tiny,
simple nematode, alive and capable of asexual reproduction. The
researchers were able to get H. mephisto to reproduce,
and the species is still "squirming around in the lab," Onstott
said. [ See
a picture of the nematode ]

The researchers found no evidence of the nematode in surface
waters or soils, indicating that it is native to deep rock
fractures. Chemical analysis revealed that the water in which
H. mephisto lives dates back at least 2,900 years,
meaning it's been down there for a while, said Rick Colwell, a
microbiologist who studies subsurface organisms at Oregon State
University.

"They have been quite careful in measuring the environment that
these organisms come from," Colwell, who was not involved in the
study, told LiveScience.

In lab experiments, the research team found that H.
mephisto prefers to snack on the bacteria found in deep rock
fractures, turning up its wormy nose at aboveground buffet
options such as E. coli.

Worms in space?

The find could encourage researchers to expand the search for
life under our own feet, said Colwell, who along with others is
working on a project called the Census of Deep Life, dedicated to
cataloguing what lies beneath Earth's surface.

"As we initiate this census of deep life," Colwell said, "I can
see expanding it in the direction of some more complex life
forms, like these nematodes."

Farther from home, the discovery of very deep multicellular worms
opens up possibilities in the
search for extraterrestrial life, said Michael Meyer, the
lead scientist for Mars exploration at NASA, who was not involved
in the study. Researchers have assumed that any
subsurface life on a planet like Mars would be unicellular,
Meyer told LiveScience.

"This kinds of opens it up to, well, even multicellular life
could be possible," Meyer said.